Prefabricated window sill unit



FIG. 1 is a perspective view of a prefabricated window sill unit showing my new design, the broken lines showing a window and wall are for illustrative purposes only and form no part of the claimed design;

FIG. 2 right side view of my prefabricated window sill unit, the left side view being a mirror image of the right side view;

FIG. 3 is front view of my prefabricated window sill unit;

FIG. 4 is back view of my prefabricated window sill unit;

FIG. 5 is top view of my prefabricated window sill unit; and,

FIG. 6 is bottom view of my prefabricated window sill unit. 

The ornamental design for a prefabricated window sill unit, as shown. 